The AIDS epidemic has become a major public health issue, with special concern about the role of injection drug use in viral transmission. A critical issue involved evaluation of the relative efficacy of alternative modes of transmission risk prevention among injection drug users (IDUs). Two broad (and not necessarily mutually exclusive) categories of prevention have evolved. The first, AIDS education/counseling, designed to increase awareness of risk and individual or social network selection of risk behaviors, is predicted on the assumption that even without structural change in the social environment of risk, IDUs can effect behavioral changes that will limit HIV transmission. Alternatively, it has been asserted that IDUs continue to engage in risk behavior despite possession of HIV knowledge, training in risk reduction skills, and strong motivation to lower risk because risk is tied to structural factors, including prescription laws, paraphernalia laws and law enforcement, and pharmacy practices. Stemming from the latter perspective has been the initiation of both legal and unsanctioned needle exchange programs. However, while there has been some evaluation of the efficacy of educational/counseling programs in lowering risk, there has been far less evaluation of needle exchange, and little comparative evaluation of the relative efficacy of these alternative models in reaching, enrolling, maintaining, and lowering risk among IDUs. The proposed prospective cohort study, called the Effectiveness of Needle Exchange in AIDS Prevention (ENEAP) project, uses multiple triangulated research techniques to compare these two modalities using existing prevention projects in Hartford, CT, namely, the Hartford Needle Exchange Program (NEP) and Project COPE (U01DA07284). Data collection will include self-report interviewing with 1,160 respondents, including out-of-treatment participants in an education/counseling program (Project COPE), participants in the Hartford Needle Exchange Project (NE), and individuals enrolled in both modalities (simultaneously or sequentially), as well as 200 IDUs enrolled in neither project. Other data collection will include ethnographic observation and field interviews in drug use scenarios, laboratory assay on needle exchange syringes, a community survey of 240 households on attitudes toward needle exchange, and process evaluation of staff attitudes and morale. Analysis will focus on determining the relative efficacy of the alternative HIV risk reduction approaches on a range of risk variables (e.g. needle "sharing," use of shooting galleries, condom use) and in light of several antecedent covariates (e.g. ethnicity, sex, age, drug of choice, duration of drug injection).